It's hard to determine who is the best among them if it's still early in the season they still have a lot to do for their new team, but if you look at his experience maybe Isak has more experience in the Premier League and has good skills when he was at Newcastle so he might be the best striker at Liverpool and might compete with his teammate Hugo Ekitike in scoring many goals because so far Hugo Ekitike has shown his abilities in the last few matches where he contributed to Liverpool victory.